A radial fan which can be considered as a typical configuration comprises a casing having a side portion and a pot-like casing portion, with an impeller wheel which is arranged in the casing and which has radially extending vanes or blades.
Such a fan for conveying gaseous media is generally used in items of equipment which involve a high flow resistance. That can involve for example a cylinder burner or a ceramic surface burner which are used in the most recent developments in gas boilers. Gas heating boilers of that kind may often involve a flow resistance of the order of magnitude of 800 Pascals and more. To ensure stable operating points, the endeavour is to produce pressure-volume characteristics which are as steep as possible, when employing a radial fan.
As an example of such a radial fan reference may be made to EP 0 410 271 A1 disclosing a unit for conveying a gaseous medium, in which the housing portion of the radial fan has a holder for an electric motor for driving the impeller wheel while the side portion is provided with an inlet opening for the feed flow of the fan air.